Acoustic Microscopy Via Scanning

We offer via posters some of the latest images recorded with the scanning acoustic microscope operating near 2.5 GHz. Our report at the 1978 Review included a description of the scanning instrument which had been scaled up in frequency to 3 GHz. This was accomplished in large part by fabricating acoustic lens with smaller radii and by heating the liquid to reduce the absorption. In our report for this year, we·will present the results of our material studies as carried out with the new instruments operating near 2.5 GHz. We will include results on four different materials - steel, Cobalt-Titanium, brass and alumina ceramic. Each of these have distinctive characteristics in the acoustic micrographs and each of these have information which is distinct from their optical counterparts

Acoustic Microscopy for Materials Characterization

An acoustic microscope with mechanical scanning and piezoelectric film transducers for the input and output has been developed for the microscopic examination of materials.1 In the reflection mode it is possible to work with an acoustic wavelength of 0.5 micrometers and a resolution that compares to that of the optical microscope. The elastic images of material surfaces as recorded with this instrument display interesting features which provide information which complements the optical microscope. In particular we find that different phases show up with good contrast and in alloy material the texture of the grains can be recorded since the grain orientation influences the acoustic reflectivity

Resonant harmonic response in tapping-mode atomic force microscopy

Cataloged from PDF version of article.Higher harmonics in tapping-mode atomic force microscopy offers the potential for imaging and sensing material properties at the nanoscale. The signal level at a given harmonic of the fundamental mode can be enhanced if the cantilever is designed in such a way that the frequency of one of the higher harmonics of the fundamental mode ~designated as the resonant harmonic! matches the resonant frequency of a higher-order flexural mode. Here we present an analytical approach that relates the amplitude and phase of the cantilever vibration at the frequency of the resonant harmonic to the elastic modulus of the sample. The resonant harmonic response is optimized for different samples with a proper design of the cantilever. It is found that resonant harmonics are sensitive to the stiffness of the material under investigation

Interdigital cantilevers for atomic force microscopy

Cataloged from PDF version of article.We present a sensor for the atomic force microscope(AFM) where a silicon cantilever is micromachined into the shape of interdigitated fingers that form a diffraction grating. When detecting a force, alternating fingers are displaced while remaining fingers are held fixed. This creates a phase sensitive diffraction grating, allowing the cantilever displacement to be determined by measuring the intensity of diffracted modes. This cantilever can be used with a standard AFM without modification while achieving the sensitivity of the interferometer and maintaining the simplicity of the optical lever. Since optical interference occurs between alternating fingers that are fabricated on the cantilever, laser intensity rather than position can be measured by crudely positioning a photodiode. We estimate that the rms noise of this sensor in a 10 hz–1 kHz bandwidth is ∼0.02 Å and present images of graphite with atomic resolution. © 1996 American Institute of Physic

Independent parallel lithography using the atomic force microscope

Cataloged from PDF version of article.Independent parallel features have been lithographically patterned with a 2×1 array of individually controlled cantilevers using an atomic force microscope. Control of the individual cantilevers was achieved with an integrated piezoelectric actuator in feedback with a piezoresistivesensor. Patterns were formed on 〈100〉 single crystalsilicon by using a computer controlled tip voltage to locally enhance the oxidation of the silicon. Using the piezoresistor directly as a force sensor, parallel images can be simultaneously acquired in the constant force mode. A discussion of electrostatic forces due to applied tip voltages, hysteresis characteristics of the actuator, and the cantilever system is also presented. © 1996 American Vacuum Societ

Contact imaging in the atomic force microscope using a higher order flexural mode combined with a new sensor

Cataloged from PDF version of article.Using an atomic force microscope(AFM) with a silicon cantilever partially covered with a layer of zinc oxide (ZnO), we have imaged in the constant force mode by employing the ZnO as both a sensor and actuator. The cantilever deflection is determined by driving the ZnO at the second mechanical resonance while the tip is in contact with the sample. As the tip‐sample force varies, the mechanical boundary condition of the oscillating cantilever is altered, and the ZnO electrical admittance is changed. Constant force is obtained by offsetting the ZnO drive so that the admittance remains constant. We have also used the ZnO as an actuator and sensor for imaging in the intermittent contact mode. In both modes, images produced by using the ZnO as a sensor are compared to images acquired with a piezoresistivesensor

Nanometer-scale patterning and individual current-controlled lithography using multiple scanning probes

Cataloged from PDF version of article.Scanning probe lithography(SPL) is capable of sub-30-nm-patterning resolution and nanometer-scale alignment registration, suggesting it might provide a solution to the semiconductor industry’s lithography challenges. However, SPL throughput is significantly lower than conventional lithography techniques. Low throughput most limits the widespread use of SPL for high resolution patterning applications. This article addresses the speed constraints for reliable patterning of organic resists. Electrons field emitted from a sharp probe tip are used to expose the resist. Finite tip-sample capacitance limits the bandwidth of current-controlled lithography in which the tip-sample voltage bias is varied to maintain a fixed emission current during exposure. We have introduced a capacitance compensation scheme to ensure continuous resist exposure of SAL601 polymerresist at scan speeds up to 1 mm/s. We also demonstrate parallel resist exposure with two tips, where the emission current from each tip is individually controlled. Simultaneous patterning with multiple tips may make SPL a viable technology for high resolution lithography. © 1999 American Institute of Physic

An Analytical Approach to the Design of Multiple Mode Rectangular Cavity Waveguide Filters

The multiple mode rectangular cavity structure with square corner cuts is revisited. An attempt to predict the physical dimensions of the cavity for dual mode second-order and triple mode third-order filters is made. Analytic expressions are formed to be used in the design process. The classical triple mode cavity filter structure is altered to give a finite frequency transmission zero either in the lower or upper sideband of the center frequency. The concept is illustrated with example designs. A novel additive manufacturing technique is used to fabricate a selected filter structure. The experimental results are in agreement with the expectations. © 2017 IEEE

Analysis and design of interdigital cantilever as a displacement sensor

Cataloged from PDF version of article.The interdigital ~ID! cantilever with two sets of interleaving fingers is an alternative to the conventional cantilever used in the atomic force microscope ~AFM!. In this paper we present a detailed analysis of the interdigital cantilever and its use as a sensor for the AFM. In this study, we combine finite element analysis with diffraction theory to simulate the mechanically induced optical response of the ID. This model is used to compare this system with the optical lever detector as used in conventional instruments by analyzing the ratio of signal to noise and overall performance. We find that optical detection of the cantilever motion with interdigital fingers has two advantages. When used in conjunction with arrays of cantilevers it is far easier to align. More importantly, it is immune to laser pointing noise and thermally excited mechanical vibrations and this improves the sensitivity as compared to the optical lever. © 1998 American Institute of Physics